In an orthogonal frequency division multiplexed (OFDM) system, carrier frequency offset (CFO) produces the same phase drift at all subcarrier indices, while sampling frequency offset (SFO) introduces a phase rotation which increases linearly with the subcarrier index. The impact of CFO and SFO are the loss of the orthogonality of the subcarrier, which results in inter-carrier interference (ICI) and the rotation of constellation points. To mitigate the impact of CFO and SFO, a two-step process is known: 1) Estimation of CFO and SFO; and 2) Correction of CFO and SFO based on the estimation.
There are three major methods for CFO/SFO estimation, as described in Z. Gao, et al, “Self-Cancellation of Sample Frequency Offset in OFDM Systems in the Presence of Carrier Frequency Offset”, IEEE VTC September 2010 Ottawa, Canada, pp. 1-5, hereby incorporated by reference in its entirety.